Rebecca Shuttleworth, who the judge said had subjected her son to a lingering death. Photograph: PA

A mother who beat her two-year-old son to death after months of horrific cruelty has been told she will serve 18 years in prison before being considered for parole.

Jailing Rebecca Shuttleworth, Mr Justice Spencer said she was a cruel, deceitful and manipulative woman who had subjected her son, Keanu Williams, to a lingering death.

He said it had been Shuttleworth's duty to protect a defenceless child, but instead she had committed a brutal killing.

A serious case review is under way to discover how Shuttleworth, 25, managed to hide her violence from the many professionals with whom she and her child came into contact.

Almost all the jurors who had heard the case against Shuttleworth returned to court to see her sentenced for murder and four counts of child cruelty.

During her six-month trial at Birmingham crown court they heard that 37 external marks of injury were found on the boy's body. He had bruising to his lower chest, abdomen and back and had suffered a fractured skull.

A postmortem examination identified "tramline" bruising consistent with Keanu having been struck with an object such as a stick or rod with some force. A fist-sized tear was discovered in part of the child's abdomen, which had caused substantial bleeding.

Keanu's lifeless body was found by paramedics in January 2011 after Shuttleworth's partner, Luke Southerton, dialled 999 claiming the boy had stopped breathing, was pale and had not been well.

It is thought the fatal injuries were inflicted two days earlier at Southerton's flat in the Ward End area of Birmingham.

Southerton, 32, was convicted of one count of child cruelty – an assault on Keanu – but cleared of murder and other offences. He was given a nine-month suspended sentence and ordered to carry out 200 hours of community service.

Following Shuttleworth's conviction on Monday, the chair of Birmingham's safeguarding children board, Jane Held, said: "It is already clear there are lessons to learn from how various agencies worked together to support Keanu and his family.

"It is clear from this trial that professionals in the different agencies involved missed a significant number of opportunities to intervene and take action."

It emerged that while Shuttleworth was on bail awaiting trial she was caught on film shouting out in delight as her new partner won a £10,000 lottery prize.